final fix - alton starter/yves mod-upgrade

My approach is to treat it like a head gasket - torque the crankshaft nut up, go for a ride and get all to running temp, torque again, repeat until the nut no longer moves.
Without Yves fix the sprag is only held in place by friction from the clamping of that nut, the key only gets the timing mark in the correct location. If the sprocket relaxes on its taper even a little bit then the clamping force drops in a hurry and chaos follows. Just my theory of course.
Best of luck.

Peter Waller said:

My woodruff key has just failed on my Alton Starter on my 850 Commando. We spent 3 hours with a disc cutter to remove the sprag clutch assembly...horrible Does anyone have any suggestions to help me when I put the new parts back on? I cannot get the Yves fix. Have purchased new sprag clutch assembly, primary chain, starter chain and new stator woodruff key. Pullers would not remove the assembly as it was unbelievably tight on the crankshaft. The last time before this when I removed it, it came off easily.

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NOTE - JUST REALIZED I HAD THE WRONG MMC LINK FOR THE BELLEVILLE WASHER - THE CORRECT PART NUMBER IS NOW SHOWN. you cannot purchase the "yves fix" parts or kit. it's a DIY mod or a local machinist/friend fabrication. while i can't 100% guarantee this, the best thing i can suggest for reassembly is to add a serrated belleville spring lock washer under the crank nut, thread locker, and increase the torque to 70-75 ft.lbs. i added the belleville washer in addition to the yves fix on my Mk2 for backup. here in the states, they are available from McMaster-Carr - https://www.mcmaster.com/90895A215/ . if you cannot locate one in the UK, contact me - email or PM. BTW Peter, failed woodruff key, been there - TWICE and i know all about destroying the sprag clutch first hand!

Thx for the info Joe. I am dreading putting it all back together because I don't understand what happened and it will probably happen again. I see that I can get those washers here in the UK can you tell me what size I need? They are all Metric size.

I see on your link it says M18. I jus searched UK Google and the largest size was M16...would this do?

Hi Baz. I have ordered the correct size and do you have any more advice before it all goes back on....thx.

Peter Waller said:

Hi Baz. I have ordered the correct size and do you have any more advice before it all goes back on....thx.

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My unhelpful advice would be to get the yvee fix
But if giving it another try as standard you really need to make sure the crankshaft and Woodruff key and keyway is spot on
Plus everything kept as tight as possible
Timing set properly
No trying to start with a crankcase full of oil etc

if anyone's interested, here's Yves original thread -- https://www.accessnorton.com/Norton...-solution-for-broken-woodruff-key-2017.24163/

don't know if i've ever posted this, but here's a big thanks to "yves norton seeley" for his original design and engineering behind the mod/upgrade.

Peter Waller said:

I see on your link it says M18. I jus searched UK Google and the largest size was M16...would this do?

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They certainly don't seem to be as widely available in the UK as over in the states, but I spotted these on ebay..


After reading this thread, I'll be wanting to use one myself when my Alton goes in